1. Field of the Invention
This invention relates generally to a method and analyzer for monitoring a chemical process. More particularly, this invention relates to a method and analyzer for monitoring the progression of a chemical reaction occurring in a chemical process using process flow injection analysis.
2. Background
In some chemical processes, particularly batch processes, it is necessary that the particular chemical reaction be terminated at a given point in time, either because the desired properties of the reaction product have been reached and further processing will diminish the desired properties, or the reaction itself could become uncontrollable or reach an unsafe condition. This may be particularly true in process involving the conversion of monomers to polymers where the specific properties of the resultant product are dependant upon the extent of polymerization.
It is thus desirable that the progress of such reactions be monitored at frequent intervals and with a great deal of accuracy so that the reaction may be timely controlled and also so that an operator will be aware of when the reaction has reached its desired limit and the necessary steps can be taken to quench or otherwise terminate the reaction.
Also, in some chemical processes, the reaction is initiated and sustained by adding a catalyst and stopped by adding a quenching agent. In such cases, it is desirable that the process be closely monitored so that the supply of the catalyst and addition of the quenching agent may be timely controlled.
Attempts to monitor such reactions by analyzing the reaction solution using known methods such as Fourier Transform infrared spectroscopy (FTIR) have not been successful. Due to the strong absorption of infrared radiation by the materials involved, FTIR analysis can only be performed using attenuated total reflectance (ATR) flow cells, which reduces absorption without effecting spectral resolution. However, the optical surfaces of the cells used to analyze a particular species of a given polymerization process can become coated with a film of polymer species which blocks the transmission of the light thus interfering with the analysis. While numerous solvent cleaning schemes have been tried to remove the coating between each series of analyses, the films appeared irreversibly coated on the optical crystals of the flow cells and only physically wiping the delicate crystals removed the coatings.